﻿116 EIGHTH ANNUAL REPORT 



must remain a matter of individual opinion, I repeat that careful 

 comparisons made during the year of many hundreds of specimens- 

 both living and dead, of spretus, femur-ruhrum^ and Atlanis fully 

 establish in my own mind the justness of the separation of these 

 three forms, and Prof. Thomas is of the same opinion. I have a box 

 full of each now before me, and no one would for a moment hesitate 

 to separate the typical, diminutive, livid, mottled and strongly marked 

 Atlanis from the typical, large, pale, more uniform and voracious- 

 looking spretus. Granted — as I freely have — that they approach each 

 other through deviations from the average, as indeed most species do,. 

 I have yet to see the first specimen of spretus and Atlanis that I could 

 not properly separate ; and when Mr. Scudder is more familiar with 

 the true Rocky Mountain spretus, he will give up his notion that it 

 occurs in different localities in the East. All such statements result 

 from confounding these two forms and the inaccuracy that such state- 

 ments imply is good evidence of the necessity of designating the twa 

 forms by different names. Indeed Atlanis is more effectually sepa- 

 rated from spretus than from femur- ruhrum^ for while it may be dis- 

 tinguished from this last by the characters which I gave a year ago,, 

 viz.: smaller size, more mottled coloring, relatively longer wings, and 

 notched anus ; and while aside from these characters, its brighter yel- 

 low venter permits its separation with great ease in life, the two forms 

 more thoroughly blend by departures from the average, than ^o spre- 

 tus and Atlanis. Thus, Mr. Thomas in speaking of them, writes : 



So far all the Atlanis 1 have spread have the wino^s slig:htly tinged with blue when 

 fresh, while this does not appear to be the case with the true femur-rubrum ; it 

 {Atlanis) also has the outer face of the posterior thighs more distinctly marked with 

 alternate oblique dariv and light bands, in these two characters agreeing very closely 

 with my C. occidentalism which is probably but a variety of femur-rubnim, iv& I am com- 

 pelled also to think your Atlanis is. I might add also that I believe Atlanis usually has 

 the hind tibia? blueish, but this character is so uncertain that it is of little value. 



1 am inclined to think femur-rubrum the older form and that during the change 

 which produced the desert condition of the west it was converted in that district inta 

 spretus. The Atlanis lorra I think is less permanent and more transient, the result 

 probably of suitable climatic conditions continued but a few years, and that as soon as 

 the climate returns to the normal condition it will revert to the usual form of femur- 

 rubrum. My C. occidentalis belongs chiefly to that region and climate found in North- 

 western Minnesota and Eastern Dakota. 



Not having previously taken Fpecimens of Atlanis in Missouri, I 

 formerly inferred that it was confined to the mountain regions of the 

 Atlantic. In 1875 I collected it in large numbers in St. Louis, Jeffer- 

 son, Washington, St. Charles, Warren, Franklin, Boone and Cole coun- 

 ties in Missouri, and in various parts of Illinois. I found it associated 

 with femur-ruhrum^ and often in equal numbers ; and this in twa 

 instances in the same fields in which the year before I had collected 

 hundreds of specimens of nothing but femur- ruhrum. 



